JavaScript Articles
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Getting lively with Firefox 90
As the summer rolls around for those of us in the northern hemisphere, temperatures are high and unwinding with a cool ice tea is high on the agenda. Isn't it lucky then that Background Update is here for Windows, which means Firefox can update even if it's not running. We can just sit back and relax! Also this release we see a few nice JavaScript additions, including private fields and methods for classes, and the at() method for Array, String and TypedArray global objects. This blog post just provides a set of highlights.
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Implementing Private Fields for JavaScript
When implementing a language feature for JavaScript, an implementer must make decisions about how the language in the specification maps to the implementation. Private fields is an example of where the specification language and implementation reality diverge, at least in SpiderMonkey– the JavaScript engine which powers Firefox. To understand more, I’ll explain what private fields are, a couple of models for thinking about them, and explain why our implementation diverges from the specification language.
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Pyodide Spin Out and 0.17 Release
We are happy to announce that Pyodide has become an independent and community-driven project. We are also pleased to announce the 0.17 release for Pyodide with many new features and improvements. Pyodide consists of the CPython 3.8 interpreter compiled to WebAssembly which allows Python to run in the browser.
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January brings us Firefox 85
To wrap up January, we are proud to bring you the release of Firefox 85. In this version we are bringing you support for the :focus-visible pseudo-class in CSS and associated devtools, , and the complete removal of Flash support from Firefox. We’d also like to invite you to preview two exciting new JavaScript features in the current Firefox Nightly — top-level await and relative indexing via the .at() method. Have fun!
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And now for … Firefox 84
As December ushers in the final curtain for this rather eventful year, there is time left for one more Firefox version to be given its wings. Firefox 84 includes some interesting new features including tab order inspection, complex selector support in :not(), the PerformancePaintTiming API, and more!
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Warp: Improved JS performance in Firefox 83
With Warp (also called WarpBuilder) we’re making big changes to our JIT (just-in-time) compilers, resulting in improved responsiveness, faster page loads and better memory usage. The new architecture is also more maintainable and unlocks additional SpiderMonkey improvements. This post explains how Warp works and how it made SpiderMonkey faster.
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Firefox 79: The safe return of shared memory, new tooling, and platform updates
Firefox 79 offers a new Promise method, more secure
target=_blanklinks, logical assignment operators, tooling improvements for better JavaScript debugging, and many other updates of interest to web developers. In addition, shared memory is back at last, with a safer implementation. -
Safely reviving shared memory
At Mozilla, we want the web to be capable of running high-performance applications so that users and content authors can choose the safety, agency, and openness of the web platform. Shared-memory multi-threading is an essential low-level building block for high-performance applications. However, keeping users safe is paramount, which is why shared memory and high-resolution timers were effectively disabled at the start of 2018, in light of Spectre. Until now...
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Compiler Compiler: A Twitch series about working on a JavaScript engine
Yulia Startsev, a JavaScript engineer on Firefox's SpiderMonkey team, introduces her new Twitch stream called Compiler Compiler. In the three opening interactive episodes, we get an inside look at how the JavaScript Specification, ECMA-262, is implemented in SpiderMonkey, by reading the spec and fixing issues in the implementation.
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A New RegExp Engine in SpiderMonkey
Regular expressions – commonly known as RegExps – are a powerful and heavily used tool for manipulating strings in JavaScript. This post describes how we updated the RegExp engine in SpiderMonkey, Firefox's JavaScript engine, by building a shim layer to V8's Irregexp. The outcome: reduced maintenance and stronger collaboration among the browsers, full support for all the new RegExp features, and compatibility with the latest ECMAScript standard.
